Anomalous reflection of visible light by all-dielectric gradient metasurfaces

Abstract

Plane wave scattering by a planar metasurface composed of two periodically alternating rectangular dielectric rods is considered. A rigorous integral equation methodology is employed for the analysis and the accurate determination of the reflected and transmitted fields. Systematic optimizations with respect to the configuration's parameters are performed, which reveal that it is possible to obtain significantly enhanced anomalous reflection (with simultaneously suppressed ordinary reflection predicted by Snell's law) with power varying from 92% to almost 100% of the input one, depending on the color of the incident light. It is shown that these reflection properties are supported by metasurfaces easily realizable with specific low-loss dielectric materials. In this way, several all-dielectric optimal designs are reported that can be used in numerous applications demanding anomalous reflection in the visible range.

Mitigating Snell's-Law reflection and transmission with metasurfaces of ordinary dielectrics

“…The latter implies also that the −1-order is reflected back in the same (second) quadrant of the plane with that where the incident field impinges on the metasurface, as well as to be transmitted back in the corresponding (third) quadrant [9]. The angle of incidence is fixed at θ = 60 o , since, as analyzed in [9], then the reflection angle (measured as the angle between the negative z-axis and the wavevector of the −1-reflected order) is close to the angle incidence θ.…”

“…The angle of incidence is fixed at θ = 60 o , since, as analyzed in [9], then the reflection angle (measured as the angle between the negative z-axis and the wavevector of the −1-reflected order) is close to the angle incidence θ. The propagation direction of the −1-transmission order is symmetric with respect to the z-axis to that of the −1-reflected order.…”

“…The range of the period Λ is that dictated by (9). The two dielectric regions of the slab are considered to be occupied by Teflon AF fluoropolymers [10] with n 1 ∼ = 1.35 and lossless Silicon with n 2 obeying the frequencyvarying models of [11].…”

“…Next, by restricting the observation vector (x, z) on the domain of the inclusions and considering the inner products of both sides of the resulting equation with the conjugates of the expansion functions in (3), we formulate an infinite non-homogeneous linear system of equations with respect to c ± n , n ∈ Z. This infinite system is solved numerically by truncation, as described in [9], yielding the coefficients c ± n for n = −N t , . .…”

Achieving Anomalous Refraction with Metasurfaces Composed by Two Ordinary Dielectric Materials

“…In [9] and [10], it was demonstrated that a gradient dielectric metasurface composed of two periodically alternating lossless materials can generate anomalous reflection phenomena in the visible frequency range; namely the power of the −1-reflected order is significantly enhanced while the corresponding powers of the 0-reflected and transmitted orders (dictated by Snell's law) are annihilated. The effective properties of the metasurface's unit cell offering these characteristics can be found in ordinary dielectrics.…”